1. Field of the Invention
The present invention relates to railroad dump cars. In particular, the present invention is a hydraulically powered system for operating the dumping mechanism of the dump car.
2. Description of the Prior Art
Side dump railroad cars are used for carrying and unloading bulk materials. The typical car comprises a frame with wheels and a pivotally connected hopper body. The body characteristically consists of side doors that open when the body is tilted at an angle sufficient to discharge the bulk material.
These present-day side-dump railroad cars are actuated by pneumatic rams that are attached to the frame of the car. Upon actuation, a piston raises the bed on one end, discharging the material over the other side of the car through the opened side door.
The source of compressed air to drive these rams is from an air compressor inside of the locomotive. A disadvantage to the use of pneumatic rams, however, is that they are (i) large, (ii) expensive to service, (iii) because they operate by air pressure, they are difficult to control and regulate under varying load conditions, and (iv), are susceptible to condensing and freezing of water vapor in the rail air lines and system components during cold winter months, thus causing blockage.
Probably most important from a safety standpoint relates to the difficulty of precisely controlling the movement of the dump body. This is because high pressure is initially required to begin the dumping process and as the load is removed, less pressure is required to complete the dumping process. When this condition occurs, the reduced compression of the air in the pneumatic ram causes a large and rapid travel in the piston, completing the dumping in an uncontrolled manner. This inability to control the rate of dumping as the load is removed causes great stress on all components of the dump car as the dump bed is slammed to the travel stops.
Others have attempted to solve this problem by replacing the pneumatic rams with hydraulic drive rams. A major disadvantage inherent in some systems, such as that depicted in McCormick, U.S. Pat. No. 4,407,202, is the use of a hydraulic accumulator attached to each railroad car to store hydraulic fluid pressure. This accumulator poses a potential safety problem, since hydraulic fluid may be at a pressure of 3000 psi or greater, a valve failure could cause the car to dump unexpectedly, having serious consequences. Therefore, a hydraulically operated side dump railroad car having a dump mechanism that operates at approximately the same rate as a car equipped with a hydraulic accumulator would be an important advancement for railroad operators.